SAN JOSE -- Silicon Valley businesses and residents were urged Tuesday to conserve electricity after gunshots damaged PG&E's Metcalf transmission substation in San Jose, a critical hub in the Bay Area transmission system.

Multiple gunshots were fired at the substation, located on Metcalf Road near U.S. Highway 101, shortly before 2 a.m. Tuesday morning. The gunshots apparently caused cooling oil to leak from a transformer bank. The leak has now been contained.

"The Metcalf substation was damaged by vandalism. There were multiple gunshots heard at the facility," said PG&E spokesman Jason King. "We have crews on the scene and we are currently assessing the situation."

The Santa Clara County Sheriff's Office, the lead agency on the case, said that PG&E contacted the Sheriff's Office at 3:46 a.m. about a breach of their security fence at the substation in the 100 block of Metcalf Road. PG&E reported that at least five transformers were damaged.

The California ISO, the agency charged with maintaining California's electric power grid, urged residents and businesses in the San Jose area to conserve electricity.

"As damage assessments continue, additional equipment at the substation may be taken out-of-service," said a statement by the California ISO. "This will limit transmission capability in this area of the high-voltage grid, which is why conservation is required."